Artificial fiber



July 19, 1949.

' J. W. HALL ETAL ARTIFICIAL FIBER Filed Oct. 3, 1944 INVENTORJ PatentedJuly 19, 1949 UNITED STATE NT OFFICE ARTIFICIAL FBER DelawareApplication October 3, 1944, Serial No. 557,004

This invention relatesv to novel hollow filaments of regeneratedcellulose, products formed therefrom, and to processes for producing thesame.

It has been proposed, heretofore, to produce hollow filaments by methodsinvolving the emulsification of air in viscose prior to extrusionthereof, or the incorporation in the viscose of substances, commonlyalkali carbonates, capable of reacting with acid to develop a gas, andextrusion of the mixture into an acid spinning bath.

All of the hollow regenerated cellulose fllaments of the prior. art,however, produced, have had a'common characteristic in that they havebeen tubular in cross-section, comprising either a hollow continuouscanal, or a plurality of individual voids or lumens each taking up theentire cross-section area of the filament and spaced end to end alongthe length of the filament by transverse partitions. The hollowfilaments oi the prior art have numerous disadvantages. Mostimportantly, such filaments have extremely low tensile strength andextensibility and, further, readily undergo considerable permanentcollapse during manufacture, such as when they are passed over guides,about the godets, and under their own pressure as they are beingcollected on bobbins or in spinning buckets. Even after drying, shouldthere be any appreciable residual inflation in the filaments having thetubular voids or lumens, additional permanent deflation occurs Wheneverarticles formed therefrom such as cushions, mattresses, wearing apparel,etc., are subjected to compression, with a noticeable loss -of buoyancyand increase in weight of the articles.

It is the purpose of our. invention to provide new hollow filaments. of.regenerated cellulose which do not exhibit the disadvantages associatedwith the hollow filaments heretofore known. It is a further object ofour invention to provide hollow filaments which undergo substantially noloss in inflation when they are manipulated during production thereof. Astill further object is to provide articles formed from our new hollowfilaments which articles are not susceptible to deterioration in use dueto loss of inflation in the filaments when they are compressed. Furtherobjects and advantages will appear hereinafter.

In accordance with our invention, hollow filaments of regenerated:cellulose are obtained which in cross section, have a unique structure 2Claims. (CI. 2882) by virtue of whichthey are sharply distinguishablefrom hollow filaments of the prior. art.

In the accompanying drawing illustrative oi the invention, g

Figure 1 is a cross-sectional view. of the file. ments of our invention;

Figure 2 is a view taken along the. length of the filaments of ourinvention; and.

Figure 3 is a cross-sectional view of a typical hollow filament of the,prior art.

Referring to Figure 1, it will be seen that our new filaments have, incross-section, a, cellular.

type structure, the cross-section area being occupied by a web-likenetwork comprising a plurality of partitions 2 which separate. anddefine a plurality of voids or.lumens.3.' The partitions 2 radiateirregularly from the solidportion at one or more points 4 withinthefilament, andconnect the solid portion 4 with what may be defined asthe inner peripheral wall of. the fiber. The partitions lay more or lessat random and may have a regular or irregular contour, and the voids orlumens, which may vary in size from extremely small to much largervoids, are of varying shape, some being more elongated than others, forexample, as determined by the con tours of the dividing partitions. Thesolid portion 4 extends longitudinally of the fiber length along atleast a substantial portion thereof. The voids 3 overlap one another andlie irregularly spaced along the fiber axis as shown in Figure 2. Theseparating partitions 2 present, as viewed in Figure 1, an essentiallyWeb-like network or configuration. All of the partitions radiate from apoint within the filament but not necessarily all from the same pointand the partitions may have a more or less complex shape constituted bya branched structure, one or more partitions branching off from one ormore others which radiate from a common point, as shown in Figure 1. Theexternal walls of the hollow filaments are thus provided with aninternal web-like support which enhances the rigidity of thefilaments sothat while they are flexible enough to enable their being easilymanipulated and adaptable to various textile working processes, they donot tend to collapse even under the influence of very high compressionalforces. Under such conditions, the filaments give, but do notpermanently collapse and upon removal or the compressing forces theinflated condition is immedi ately recovered.

We have discovered that filaments having the novel structure, incross-section, described above and shown in Figure 1 can. be producedfrom viecose containing sodium carbonate only by a proper, selectivecontrol and correlation of the spinning conditions.

Generally, the viscose should analyze from about 1.9 to about 2.5% totalsulfur, from about 6 to 9% sodium hydroxide (based on percent weight inviscose), from about 6 to 9% by weight cellulose, and should contain alarge proportion of sodium carbonate, that is, from about to (based onthe cellulose present). The viscose preferably should have a common salt(NaCl) point of from 5 to 6.

The viscose is extruded into an acid bath having a regenerating capacityequivalent to not less than 11% sulfuric acid, mixed with a largeproportion, not less than 5%, of a zinc salt, and a large proportion ofsodium sulfate, that is not less than 21%. Preferably, the bath containsfrom about 11.3 to 12.5% sulfuric acid; from about 5 to 6% zinc sulfate;and from about 21 to 25% sodium sulfate. The viscose may contain specialmodifying agents, if desired, such as dyes, pigments, etc., or anymixture of such materials.

The spinning bath should have a temperature between 40 to 60 C. Theimmersion depends, to some extent, upon the denier of the filaments,longer immersion periods being productive of better results in the caseof filaments of larger total denier and denier per filament.

If desired, the filaments may be given a stretch up to about 40 to oftheir length, by passing them between godets or rollers operating atdifferent speeds, or by means of any other equivalent stretchingprocedure, and preferably the filaments are stretched soon after leavingthe coagulating medium. When necessary, the stretching may befacilitated by passing the filaments through a plasticizing bath, suchas hot water, hot acids, and the like.

Generally, the various factors involved in producing the fibers arecorrelated as indicated, and the various ingredients of the viscose andthe spinning bath are used in proportions within the ranges stated, butwhen the sodium carbonate is present in the viscose in the higheramounts, the sulfuric acid, zinc sulfate, and sodium sulfate contents ofthe spinning bath are not quite as critical as when the smallerquantities of sodium carbonate are employed.

For illustrative purposes, the following specific examples are given.

Example I A viscose aged to a common salt point of 5.5 and having 8.4%by weight sodium hydroxide, 7.3% cellulose, 2.3% total sulfur and towhich had been added 25% by Weight of sodium carbonate (based oncellulose) was extruded through a spinneret to produce a 120-filamentthread having a total denier of 300, into a spinning bath maintained at50 C. and containing 12.3% sulfuric acid, 22% sodium sulfate and 5.3%zinc sulfate.

The immersion was 24". After leaving the bath the filaments were passedover two godets in succession having a differential in speed whicheffected a 40% stretch of the filaments. Filaments which along theirentire length showed, in cross-section, a cellular type structure wereobtained.

Example If A viscose aged to a sodium chloride salt point of 5.3, andhaving 8.1% by weight sodium hydroxide, 7.4% by weight cellulose, 2.3%by Weight total sulfur and to which had been added 20% of sodiumcarbonate (based on cellulose present) was extruded through a spinneretto produce a 200 filament thread having a total denier of 300, into aspinning bath maintained at about 45 C., and containing 12% sulfuricacid; 22.5% sodium sulfate, and 5.3% zinc sulfate. The immersion was 14inches. The filaments were stretched 40% between godets. Filaments whichalong of the fiber axis showed, in cross-section, a cellulartypestructure, were obtained.

Example III A viscose aged to a sodium chloride salt point of 5, andhaving 9% by weight sodium hydroxide, 7.6% by weight cellulose, 2.3% byweight total sulfur and to which had been added 25% of sodium carbonate(based on the cellulose) was extruded through a spinneret to produce a490- filament thread of 1200 total denier, into a spinning bathmaintained at 50 C., and containing 11.4% sulfuric acid, 23% sodiumsulfate, and 5.5% zinc sulfate. The immersion was 14", The filamentswere stretched 40% between godets. Filaments were obtained which, along95% of their length showed, in cross-section, a cellulartype structure.

Example IV A aged to a SOdlllIIl chloride salt point 5.5, and having8.5% by weight sodium hydroxide, 7.2 cellulose, 2.3% total sulfur and towhich had been added 25% sodium carbonate ased on the cellulose present)was extruded through a spinneret to produce a 24 filament structure of300 total denier, into a spinning bath containing 12% sulfuric acid,22.5% sodium sulfate, and 6% zinc sulfate. The immersion was 64". Thefilaments leaving the bath were given a stretch of 40%. The filamentsthus obtained showed, in cross-section, at all points along the filamentlength, a cellular type structure.

The filaments obtained as described have dry tensile strengths ofapproximately 2 or more grams per denier, and wet extensibilities ofabout 30%.

The individual filaments produced in accordance with this invention havein cross-section a cellular type structure at points along at least asubstantial portion of the filament length which comprises a pluralityof voids or gas pockets which are separated by partitions forming aninternal support for the filaments.

The hollow continuous filaments initially obtained may be cut to staplelength, as well as continuous or broken filament yarns. For example, thefilament bundles proceeding from several spinnerets over stretchinggodets may be combined into tows of 1200 up to 400,000 or so denier. Thetows while still Wet are cut to staple fiber, which is allowed to fallinto a liquid bath which may serve merely to effect opening of the fiberclumps, or may also serve the purpose of an additional liquid treatment,such as washing or desulfurizing. The opened staple fibers arewettreated, and finally dried in any appropriate manner.

The filaments have a delustered appearance, give full, deep dyeings indull shades, and are characterized by a soft hand and feel, excellentwater retentivity, light weigh-t, and enhanced covering power. Thosefilaments that are made without much stretching are generallysubstantially cylindrical or long and oval in cross-section,

depending upon the type of spinneret utilized, while those which havebeen given a greater amount of stretching exhibit numerous points ofnecking down along their length, and due to this irregularity ofconfiguration possessed by some of the filaments they exhibit fullingand felting properties resembling natural wool.

The new hollow fibers, either as continuous filaments or as staplefibers may be used in the production of textile yarns and knitted orwoven fabrics which are especially useful in the manufacture of wearingapparel or bed clothing where lightness in weight, buoyancy, andprotection from cold or heat are important factors. Carded mats of thematerial may be used as fillers for the production of comforts, wearingapparel, cushions, life preservers, vibration damping, sound insulatingor generally as a heat insulating material for filling spaces betweenthe walls of buildings or other structures to be insulated, such as iceboxes, cold rooms, ships, railway cars, automobiles, airplanes, and thelike, and for any of these uses, Where desired or necessary, the matsmay be provided with a water-proof wrapping or the filaments may beimpregnated with a resin, such as phenol-aldehyde and phenol-ketoneresins, for example, phenol-formaldehyde resins, phenol-diphenylolpropane-formaldehyde or ketone resins, phenol-furfural resins, aromaticsul-= fonamide-aldehyde resins, benzophenone aldehyde resins, and thepolymerized vinyl resins.

The novel hollow filaments of the present invention, may be incorporatedin filamentary bundles of the type described in the copendingapplication of Robert J. Taylor, Serial No. 530,682, filed April 12,1944, now Patent No. 2,461,094, Feb-- ruary 8, 1949.

The filaments either per se or in the form of a yarn-like bundle, or inthe form of a mat, carded or otherwise, may be crimped by efiectingshrinkage, which increases the bulk of the products. Further thefilaments may be rendered potentially self-crimpable by stretching themwhile in a plasticized condition, removing the plasticizer while thestretched condition is maintained, fabricating the stretched filamentsor fibers and permitting the development of crimp therein in situ in thefabricated structure by activating the filaments, as during a fulling orfelting operation, and permitting the crimped filaments or fibers to drywhile relaxed.

Since many variations and modifications may be made in practicing thepresent invention, it is to be understood that we are not to be limitedexcept b the spirit and scope of the appended claims.

We claim:

1. A yarn comprising a bundle of inflated regenerated cellulose fibers,a plurality of which show in cross-section, along at least a substantialportion of its length, a web-like network constituted by a plurality ofdistinct radiating partitions which separate and define a plurality ofdistinct individual voids between an internal point and the peripherywall of the fiber, the partitions constituting an internal support forthe peripheral wall of the inflated fiber.

2. A stretched, inflated regenerated cellulose fiber of from about 1 to15 deniers and showing, in cross-section, along at least a substantialportion of its length, a web-like network constituted by a plurality ofdistinct radiating partitions which separate and deflne a plurality ofdistinct individual voids between an internal point and the peripheralWall of the fiber, the partitions constituting an internal support forthe peripheral wall of the inflated fiber, and the fiber having a drytenacity of approximately 2 gm. per denier.

JAMES W. HALL. ALFRED W. HUNTER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 20,953 Stoeckly Dec. 20, 19381,487,807 Rousset Mar. 25, 1924 1,867,298 Zart July 12, 1932 2,136,463Picard Nov. 15, 1938 2,136,464 Picard Nov. 15, 1938 2,171,805 PicardSept. 5, 1939 2,339,950 Sackner Jan. 25, 1944 2,399,260 Taylor Apr, 30,1946 FOREIGN PATENTS Number Country Date a 260,872 Great Britain Nov.11, 1926 282,973 Great Britain Jan. 5, 1928 318,632 Great Britain Sept.5, 1929 343,604 Great Britain Mar. 5, 1931 OTHER REFERENCES RayonTextile Monthly, Oct, 1942, page 33, Continuous Cellophane Bubble Yarn.

